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Coaxial line-to-circular waveguide transitions are characterised by numerical modelling supported by experimental verification. Various coaxial line to waveguide diameter ratios have been considered, and the effects of parameter variations have been studied. It has been found that both narrowband matching at a specific frequency and broadband matching over the entire operating frequency band can be achieved. The optimum parameters for such transitions are reported.

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At present, Light Emitting Diode (LED) has been widely used in many fields. As illumination requirements on certain occasions are strict, an optical structure must be designed to distribute light. In this study, we propose a freeform reflector design method for uniform illumination. According to the radiation characteristic of LED and the illumination requirements, a differential equation is established. The numerical solution of the equation can determine the positions of the points on the reflector. The coordinates of these points are input into three-dimensional modeling software to fit the reflector. The optical system has been simulated with a ray tracing method. The simulation result shows good uniformity of illumination. If we apply this method to one computer program, and then the computer finishes the preliminary design, it will significantly reduce the design time. It can also be used in reflector design for non-uniform illuminance.